The invention relates to power supplies, and more particularly, to testing of power supplies.
A typical conventional large-capacity “on-line” UPS may include an AC/DC converter (e.g., a rectifier) that is configured to be coupled to an AC power source, such as a utility source, and a DC/AC converter (e.g., an inverter) that is coupled to the AC/DC converter by a DC link and which produces an AC voltage at an output (load) bus of the UPS. The UPS may further include a bypass circuit, e.g., a static switch, which can be used to couple the AC power source directly to the output bus of the UPS, such that the AC/DC converter and DC/AC converter are bypassed. The bypass circuit can be used, for example, to provide an economy mode of operation and/or to provide power to the load when either or both of the converters are damaged or inoperative.
Factory testing of such a UPS is often performed with a resistive, reactive load and/or a non-linear test load. Performing such tests may require extensive infrastructure, including the loads themselves and a sufficiently high-capacity utility infrastructure to supply the power for the testing. Additionally, significant energy costs may be entailed in such testing, as the energy delivered to the test load in load testing is often dissipated as heat. Such costs may be replicated when the UPS is installed at the customer's premises, where a commissioning test may be performed at installation to ensure that the UPS and associate power delivery components, e.g., lines, switches, breakers and the like, operate as intended at rated load.
Techniques for recycling energy in UPS bum-in testing are described in articles entitled “The Burn-in Test of Three-Phase UPS by Energy Feedback Methods,” by Chen et al., PESC 93 in Seattle Wash., U.S.A., (1993), and “Self-load bank for UPS testing by circulating current method,” by Chu et al., IEE Proc.-Electr. Power Appl., Vol. 141, No. 4 (July 1994). Each of these techniques, however, utilize specialized test equipment that can lead to extra cost, and which can make the test techniques less useful for field testing.